Lightweight Architectural Panels by Ken Baur, Director of Research and Development & Technical Sales Support

For the past year, High Concrete has been aggressively testing a new type of lightweight architectural panel which is now part of our product offering.  The panel is comprised of a thin concrete face (1.5”) that is strengthened by a series of concrete ribs around the perimeter of the panel.  The ribs occur within the panel at 4’ on center.  The thin face is made possible by using a layer of carbon fiber mesh which is compatible with concrete, and cannot deteriorate or corrode.  Carbon fiber is a very high strength material which has been developed into a reinforcing mat.  This work was completed through a combined effort of High Concrete Structures working along with three other precast companies and a composite fiber manufacturer.  Because the mesh is non-corrosive, it can be used with very little concrete cover, making the thin face possible.  Composite carbon reinforcement is addressed within ACI Committees Report 440.1R-01.

This panel will weigh only about 30 lbs. per sq. ft. as compared to a normal 6” thick architectural panel, which would weigh 75 lbs. per sq. ft.  The lighter weight will reduce foundation and column loads.  The light weight will also cause reductions in shipping and erection costs, which will assist in making this a very competitively priced panel.  The non-corrosive nature of the carbon fiber mesh will also help to reduce long-term maintenance costs as compared to traditional steel reinforced panels. 

Finishes and shapes, which are available in normal precast panel, will also be available with this panel.  Likewise, wind connections with this new panel will be identical to those of a normal precast panel.  The bearing connections will be similar, but lighter in weight.

Please contact the High Concrete sales department or Ken Baur for further information at 1-800-PRECAST.

 

Shear Wall Framing Methods by Ned Schneider, Senior Engineer

The use of shear walls to provide lateral stability has proven to be the most efficient and cost effective way to design precast parking structures.  High Concrete Structures, Inc. typically designs the ramp area with interior load-bearing lite-walls to resist the lateral loads present perpendicular to the tee span.  Shear walls are then added parallel to the tee span for lateral stability.  In many cases, the shear walls are located on the exterior of the structure; a configuration that allows for a more open interior as well as architectural interest.

Precasting the shear walls on the exterior does present some design challenges.  Usually these walls are framed with both non-load bearing spandrels and load bearing inverted tee girders—a real design concern to incorporate into exterior shear walls.  At times, built up column sections and exposed steel connections have been incorporated into the shear walls in order to affix these components.  Although a proven solution, this has shown to be more costly and not as aesthetically pleasing. 

High Concrete has found that the more economical way to handle this situation is to provide a sixteen-inch thick shear wall at these locations.  With a thicker shear wall, pockets can be provided that will create a solid load bearing structure for framing the spandrels.  With this solution, the typical lateral connections can be used for the spandrel to wall connection and have proven to perform quite well.  The use of High Concrete Accessories is also recommended instead of traditional patches that are known to shrink and crack.  Aesthetically, the added wall thickness can be offset to the outside of the structure.  This allows the spandrel to frame in behind the wall and a clean vertical line is achieved where the two elements join.  For a more traditional look, where the spandrel is framed into a column, the added wall thickness can be offset to the inside of the structure. 

To help determine which framing system best suits your specific needs, please contact High Concrete Group at 1-800-PRECAST.

 

Vector Connector by Ken Baur, Director of Research and Development & Technical Sales Support

In the spring of 2001, High Concrete began the use of a new stainless steel connection for our double tees.  The device we are now using is produced by JVI of Chicago; its trade name is the “Vector Connector”.

Our selection of this connector was based upon testing which was completed at the University of Wisconsin.  The Vector Connector performed very well in comparison to alternatives and was about equal in capacity to our previous stainless steel connection.

We currently use the Vector Connector whenever stainless steel flange connections are specified (about 65% of our projects).  Due to an automated fabrication process, this connector is less costly than our previous stainless steel device.  The Vector Connector adds about $.03 per square foot to the cost of a tee, while our previous device added about $.07 per square foot.

This reduction in the price makes stainless steel an appealing solution for garages.  Stainless steel improves the durability of these connections and reduces long-term maintenance costs.

Please contact the High Concrete sales department or Ken Baur for further information at 1-800-PRECAST.